1. Technical Field
The present invention relates generally to an illumination device and, more particularly to a Light Emitting Diode (LED) illumination device.
2. Description of the Related Art
In one aspect, many displays used in projection and direct viewing systems operate on the basis of polarization. Such displays include reflective displays such as LCoS (Liquid Crystal on Sillicon), super twisted nematic, and ferroelectric as well as transmissive displays, such as thin film transistor (TFT), poly-silicon, and Silicon-on-Insulator. These displays can produce a high resolution image by changing the polarization state upon reflection or transmission of incident light. In particular, for example, in an LCoS display, in the dark state, a pixel reflects all light with substantially no change in polarization. In the bright state, the pixel rotates the polarization state of reflected incident light to the corresponding orthogonal state. By illuminating the display with polarized light and then filtering out nearly all reflected or transmitted light of that polarization, the display image can be viewed by the human eye or projected onto a viewing screen.
In another aspect, in recent years, the LED has been widely used for illumination due to small power consumption and long life span, as well as enhanced reliability and durability. However, light directly emitted from a LED is not polarized and uniform enough, and therefore is not satisfied to directly apply for displays used in the projection and direct viewing systems.
Therefore, what is needed is to provide a LED illumination device capable of producing uniformly polarized light and thus suitable for displays used in projection and direct viewing systems.
Other objectives, features and advantages of the present invention will be further understood from the further technological features disclosed by the embodiments of the present invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention.